TypeScript/tests/cases/compiler/inKeywordTypeguard.ts

class A { a: string; }
class B { b: string; }

function negativeClassesTest(x: A | B) {
    if ("a" in x) {
        x.b = "1";
    } else {
        x.a = "1";
    }
}

function positiveClassesTest(x: A | B) {
    if ("a" in x) {
        x.b = "1";
    } else {
        x.a = "1";
    }
}

class AWithOptionalProp { a?: string; }
class BWithOptionalProp { b?: string; }

function positiveTestClassesWithOptionalProperties(x: AWithOptionalProp | BWithOptionalProp) {
    if ("a" in x) {
        x.a = "1";
    } else {
        x.b = "1";
    }
}

class AWithMethod {
    a(): string { return ""; }
}

class BWithMethod {
    b(): string { return ""; }
}

function negativeTestClassesWithMembers(x: AWithMethod | BWithMethod) {
    if ("a" in x) {
        x.a();
        x.b();
    } else {
    }
}

function negativeTestClassesWithMemberMissingInBothClasses(x: AWithMethod | BWithMethod) {
    if ("c" in x) {
        x.a();
        x.b();
    } else {
        x.a();
        x.b();
    }
}

class C { a: string; }
class D { a: string; }

function negativeMultipleClassesTest(x: A | B | C | D) {
    if ("a" in x) {
        x.b = "1";
    } else {
        x.a = "1";
    }
}

class ClassWithUnionProp { prop: A | B }

function negativePropTest(x: ClassWithUnionProp) {
    if ("a" in x.prop) {
        let y: string = x.prop.b;
    } else {
        let z: string = x.prop.a;
    }
}

class NegativeClassTest {
    protected prop: A | B;
    inThis() {
        if ("a" in this.prop) {
            let z: number = this.prop.b;
        } else {
            let y: string = this.prop.a;
        }
    }
}

class UnreachableCodeDetection {
    a: string;
    inThis() {
        if ("a" in this) {
        } else {
            let y = this.a;
        }
    }
}